DOI: 10.1016/j.tecto.2020.228513
论文题名: Depth dependent azimuthal anisotropy in Madagascar island from ambient noise tomography
作者: Adimah N.I. ; Padhy S.
刊名: Tectonophysics
ISSN: 00401951
出版年: 2020
卷: 789 语种: 英语
中文关键词: Ambient noise tomography
; Azimuthal anisotropy
; Heterogeneity
; Lithospheric deformation
; Madagascar
; Neighbourhood algorithm
英文关键词: Acoustic noise
; Anisotropy
; Regulatory compliance
; Seismology
; Shear waves
; Tomography
; Velocity
; Wave propagation
; Ambient noise tomographies
; Anisotropic velocities
; Azimuthal anisotropy
; Broad-band seismic stations
; Dispersion measurements
; Ocean bottom seismometer
; Precambrian basement
; Rayleigh-wave phase velocity
; Shear flow
; ambient noise
; asthenosphere
; crustal structure
; Rayleigh wave
; seismic anisotropy
; seismic noise
; seismic tomography
; upper mantle
; upwelling
; Madagascar
英文摘要: To gain better insight into the structure and complex deformation pattern of Madagascar island, we derived a 3-D heterogeneous and anisotropic velocity model of its crust and uppermost mantle based on ambient noise analyses. The data set comprises ~1 year of seismic ambient noise recorded by 63 broad-band seismic stations deployed in and around the island. Data from Ocean Bottom Seismometers were treated for tilt and compliance noise before applying the standard noise processing routine followed by cross-correlation, dispersion measurement, Rayleigh-wave phase-velocity tomography in period range 5–40 s, and 3-D shear wave velocity modelling to 70 km depth. At shallow to mid-crustal depths, our results show fast velocities all over the Precambrian shield of the eastern two-thirds of the island in contrast to the adjacent west coast that is delineated by slow speeds that correlate with the sedimentary basins. In the lower crust and uppermost mantle, relatively fast velocities preponderate the western third of the island indicating a thinned crust and uplifted mantle. We found complex spatial and depth variation in patterns of azimuthal anisotropy across the island. The orientation of fast azimuth is relatively similar in the upper and middle crust. Aligning mostly N-S in the south and approximately NE-SW in the northern areas, it is attributed to alignment of cracks and metamorphic layering that pervades the Precambrian basement. The fast polarization axis in many sub-regions in the lower crust differs from that in the upper to middle crust and uppermost mantle. Apart from the dominant NE-SW fast axis observed in the uppermost mantle consistent with mantle flow, a semi-circular pattern of anisotropy coinciding with widespread intense slow velocities is observed beneath the central Antananarivo terrane. A delaminating lower crust that is initiated by an upwelling asthenosphere hypothesized for this region is invoked to explain our observation. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/170536
Appears in Collections: 气候变化与战略
There are no files associated with this item.
作者单位: National Geophysical Research Institute (Council of Scientific and Industrial Research), Uppal Road, Hyderabad, 500007, India; Academy of Scientific and Innovative Research (AcSIR), AcSIR Headquarters CSIR-HRDC Campus, Postal Staff College Area, Sector 19, Kamla Nehru Nagar, Ghaziabad, 201002, India
Recommended Citation:
Adimah N.I.,Padhy S.. Depth dependent azimuthal anisotropy in Madagascar island from ambient noise tomography[J]. Tectonophysics,2020-01-01,789